Hey Akashi,
I kept thinking about this patch and remembered why I didn't made the change
you are suggesting now.
The problem is when you only check for kbuf->mem you are excluding address 0,
which might be a valid address to load the kernel to. On s390 this is actually
done when the kernel is not loaded via a boot loader. For kexec_file however,
we cut off the first few kB of the image and jump directly to 'startup'. So
checking for !0 does not cause a problem here.
Anyway, the long term safer solution would be something like
#define KEXEC_BUF_MEM_UNKNOWN (-1UL)
for architectures to tell common code to search a fitting mem hole.
Back then I didn't do the change because I had the other workaround, which
didn't require a common code change. But when you are touching the code now it
is worth thinking about it.
Just wanted to let you know
Philipp
On Wed, 1 Aug 2018 16:58:07 +0900
AKASHI Takahiro <takahiro.aka...@linaro.org> wrote:
> Since s390 already knows where to locate buffers, calling
> arch_kexec_mem_walk() has no sense. So we can just drop it as kbuf->mem
> indicates this while all other architectures sets it to 0 initially.
>
> This change is a preparatory work for the next patch, where all the
> variant memory walks, either on system resource or memblock, will be
> put in one common place so that it will satisfy all the architectures'
> need.
>
> Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
> Reviewed-by: Philipp Rudo <pr...@linux.ibm.com>
> Cc: Martin Schwidefsky <schwidef...@de.ibm.com>
> Cc: Heiko Carstens <heiko.carst...@de.ibm.com>
> Cc: Dave Young <dyo...@redhat.com>
> Cc: Vivek Goyal <vgo...@redhat.com>
> Cc: Baoquan He <b...@redhat.com>
> ---
> arch/s390/kernel/machine_kexec_file.c | 10 ----------
> kernel/kexec_file.c | 4 ++++
> 2 files changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/arch/s390/kernel/machine_kexec_file.c
> b/arch/s390/kernel/machine_kexec_file.c
> index f413f57f8d20..32023b4f9dc0 100644
> --- a/arch/s390/kernel/machine_kexec_file.c
> +++ b/arch/s390/kernel/machine_kexec_file.c
> @@ -134,16 +134,6 @@ int kexec_file_add_initrd(struct kimage *image, struct
> s390_load_data *data,
> return ret;
> }
>
> -/*
> - * The kernel is loaded to a fixed location. Turn off kexec_locate_mem_hole
> - * and provide kbuf->mem by hand.
> - */
> -int arch_kexec_walk_mem(struct kexec_buf *kbuf,
> - int (*func)(struct resource *, void *))
> -{
> - return 1;
> -}
> -
> int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
> Elf_Shdr *section,
> const Elf_Shdr *relsec,
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 63c7ce1c0c3e..bf39df5e5bb9 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -534,6 +534,10 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
> {
> int ret;
>
> + /* Arch knows where to place */
> + if (kbuf->mem)
> + return 0;
> +
> ret = arch_kexec_walk_mem(kbuf, locate_mem_hole_callback);
>
> return ret == 1 ? 0 : -EADDRNOTAVAIL;
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